Stabilization of photographic emulsions sensitized with gold compounds



Patented May 27, 1952 POUNDS Fienry C. Yutzy and john A. Leermakers, Rochester, N. Y., assignors to Eastman Kodak Company, Roehe'ster, N. Y., a corporation of New Jersey No Drawing. Application September 24, 1949, Serial No. 117,718

20 Claims. (Cl. 95-7) This invention relates to sta-bilizationof ph'otographic emulsions which aresensiti'zed with gold compounds.

It is known that photographic silver halide emulsions can be sensitized by digesting the emulsions in the presence of gold compounds. The gains in speed thus obtained are clearly of value, but it has been found that coatings of such emulsions on the usual supports tend to lose speed on keeping or storage.

We have now found that the speed stability of coatings of emulsions sensitized with gold compounds can be markedly improved by the addition of water-insoluble gold -compounds to the gold-compound-sensitized emulsions after 'the final digestion of the emulsions but before coating the emulsions on asupp'ort. The addition of the water-insoluble gold compounds after final digestion but before coating does not increase the initial speed of the emulsion, but rather stabilizes the already sensitized emulsion against speed loss on keeping 'or storage of the coated emulsion.

It is accordingly, anobject of our invention to provide photographic emulsions sensitized with gold compounds, which emulsions haveimprov'ed resistance to loss of speed, i. e. sensitivity, on keeping or storage. A further object is to provide a p'ro'ce'ss for preparing suchimproved-emulsions. Other objects will become'apparen't hereinafter.

The usual procedure for preparing photographic silver halide developing-out emulsions, especially photographic gelatino-silver-halide developing-out emulsions. comprises the following steps:

(1) Precipitation, wherein the silver halide is precipitated by the interaction of a watersoluble silver salt and a water-soluble halide, in the presence of a carrier, e. g. gelatin. Digestion, wherein the above precipitate is heated for a period of time at a raised temperature, e. g. 50 to 60 C.-, with or without the addition of further carrier, e. g. gelatin. Washing, wherein the digested, solidified or set (e. g. by chilling) "emulsion is washed to remove soluble salts.

Melting out and second digestion, wherein the washed emulsion an'd'the resulting flowable emulsion is heated for a'period of time, with or without the addition of further carrier, e. g. gelatin.

Of course, variations of the above four'steps can be employed. An emulsion, when used without employing :a step, such *as ('3), we call an unwashed. finished emulsion. An emulsionwhen used following completion o'f'all four steps, we

call a washed, finished emulsion. The latter is the type of emulsion generally used.

During the last step, i. e. the melting-out and second or final digestion, the emulsion increases in sensitivity. To increase the speed of photographic emulsions, various substances have been added at various'stages in the preparation of the emulsions. Usually the additions are made during one of the digestion periods. Frequently sulfur compounds, i.'e. so-called sulfur sensitizers have been added, e. g. allyl isothiocyanate, thiourea, thiocarbanilide, etc., have been added. More recently, it has been proposed to employ ammonium and/or metal thiocyanates for this purpose. Still more recently gold compounds have been proposed for the same purpose. It is with these photographic silver halide emulsions which during their preparation have been sensitized by digestion in the presence of gold compounds with or without the additional presence of a sulfur sensitizer, that our invention is concerned.

In accordance with our invention, we incorporate in a photographic silver halide emulsion (which during its preparation has been sensitized by digestion in the presence ofa-gold compound) at least one water-insoluble gold compound which has a solubility in water not greater than the equivalent of 1.0 mg. of gold per ml. of water at 25 C., after the final digestion of the emulsion and before coating theemulsion on a support. Gold compounds having a solubility in water as low as the equivalent of 0.03 mg. per i 100 ml. of water at 25 'C. can be employed, as can compounds of still lower solubility.

Typical of the water-insoluble gold compounds are:

III

The water-insoluble gold compounds can be added to the emulsions in the form of solutions in suitable solvents, e. g. acetone, methyl alcohol, acetic acid, pyridine, or as dispersions in colloids, such as gelatin, polyvinyl alcohol, partially hydrolyzed cellulose acetate, casein, etc., or without any solvent or colloid. The water-insoluble gold compounds should, of course, be thoroughly dispersed throughout the emulsions, e. g. by stirring.

Ordinarily, it is advantageous to employ a concentration of the water-insoluble gold compound equivalent to from 2.5 to mg. of metallic gold per 1000 g. of silver nitrate used in preparing the emulsion. However, lower or greater concentrations can be employed, e. g. a concentration equivalent to 1000 mg. of metallic gold per 1000 g. of silver nitrate used in preparing the emulsion.

The water-insoluble gold compounds are advantageously added to the emulsions after final digestion, but prior to coating the emulsions on a support. at a pH of from 5 to 9, and most advantageously at a pH of from 6 to '7.

4 The following examples will serve to illustrate further the manner of practicing our invention.

EXAMPLE 1 A batch of gelatino-silver-bromoiodide emulsion was prepared as described by Trivelli and smith, Phot. J. 79, 330 (1939), using a precipitation time of 20 minutes (emulsion No. 11, page 330), except that just before the final digestion of the emulsion, potassium chloroaurate (KAuCh) in a concentration equivalent to 6.5 mg. of metallic gold per 1000 g. of silver nitrate employed in preparing the emulsion, thiosinamine in a, concentration of 50 mg. per 1000 g. of silver nitrate employed in preparing the emulsion, and sodium thiocyanate in a concentration of 1 g. per 1000 g. of silver nitrate employed in preparing the emulsion were added to the emulsion. A portion of the emulsion was coated on a cellulose acetate film and dried. The film was cut into two portions. One portion was kept no longer than for the short time (few hours) at about 70 F. required for the routine of exposing the film in a To sensitometer at ,4 second exposure, using watt, sunlight quality illumination and developing the exposed film in Eastman Kodak Companys D-19 developer for 4 minutes at 20 C. The results of this exposure and development are given in Table A below. The other portion was subjected to an accelerated keeping or incubation treatment wherein the coated film was stored or kept for '7 days at F. At the end of this period, the incubated film was exposed and developed as described above. Results are recorded in Table A below.

To further portions of the same emulsion after final digestion and before coating the portions of emulsion on cellulose acetate films various waterinsoluble gold compounds were added as shown in Table A below. The coated films were cut into two portions and one portion exposed and developed in the routine manner described above. The other portion was subjected to an accelerated keeping or incubation treatment wherein the coated film was stored or kept for '7 days at 120 F. At the end of this period, the incubated film was exposed and developed as described above. Results are recorded in Table A below.

Table A Water-insoluble 26% $1??? K 1 T (1 er in igeseep ng reat- Spec tion, (mg. of gold per merit (l/i) Gamma 1000 g. of silver nitrate) routine 77 0. 93 0. 05 g a; 35 l9 7 2 .06 7days at l20F 47 0. 8a 0.21 3 X 15 {routine 71 1.03 0.07 1 7 days at l20l1 88 0.90 0.24 4 X 50 {routine 52 1.13 0.11 7 days at 120Fl 25 0.36 0. S4 rou ine 5 0. B 0. 5 5 {7 datys in 120l 4g g5 30 u in 6 5 5 6. XI, 5.0 t g g rou ine 2 l. 1 5 XI, {7 da s at 120F 9g rga (1 8 rou ine 5 l. 7 4 X1150 {1 days at 120 s.... 82 0.98 0.18

From the data in the foregoing table, it is apparent that the emulsion which was sensitized by digesting in the presence of the gold compound, thiosinamine and sodium thiocyanate had a high initial speed of 77 as shown at 1. After subjecting this emulsion to an accelerated keeping treatment, however, the emulsion had lost a very large fraction of its speed (sensitivity) as shown at 1.

ace-mes 02 35 AuCh was addedto the same emulsion, in a concentration equivalent to 50mg. of gold, after final digestion but before coating the initial speed ('73') of theemulsion was reduced to only 47; after the same accelerated keeping treatment, as shown at 2. When the above-formulated water-insoluble gold compound was added to the same emulsion, in a concentration equivalent to 15 mg. of gold, after final digestion but before coating, the initial speed of 71 was not reduced at all after the same keeping treatment, as shown at'3. Actually in this last instance, there was a gain rather than a loss in speed after the accelerated keeping treatment. It is to be understood, of course, that the accelerated keeping treatment is drastic and that such severe conditions would rarely be encountered in practical keeping or storage of produots comprising sensitized emulsions. The other data-given i-nthe above table at 4" to-8 show further' the beneficial retardation or loss of speed thatcan be attained in accordance with our in- VQIltlOIl: 1a

A, batch ofgelatino-silver-bromoiodide emulsion; was,- prepared as described by Trivelli and Smith, Phot. J. 79, 330 (1939), using. a precipita tion; time of about- 20 minutes-(emulsion No. 11,

page 330), except that-justbeiorethe final digestion of the emulsion potassium chloroaurate, and sodium thiocyanate we-readded to the emulsion in the concentrations shown in Example 1. A

portion of the emulsion was coated on cellulose acetate film and dried. The film was cut into two portions and the one portion exposed and de-- veloped in the routine manner shown inExample 1 while the other portion was incubated and then exposed and developed as shown-inExample 1. Results are recorded in Table B below.

'Io further portions of'the same emulsion after finaldigestion and before coating the portions of emulsionj on cellulose acetate films various water-insoluble gold compounds" were added as. shown inTable B'below; The coated .fiiins were out" into two portions and one portion exposed and developed in the routine manner described in Example 1; The other portions were, incubated an'dth'e'n exposed and developed as described in Example 1. Results are recorded in Table 13 below. Water-insoluble r i i h T s d ter inc iges- 'ecping roe.- spee tion (mg. of gold per ment (1/1) Gamma Foe 1000 g. of silver nitrate) routine 49 0. 61 0. 02 ways at10F :15, 1.151,, 0.07 9 H 0 48: 0.60 0.02 ,{1 ii ii g 4; 2 nfzllm -10 0. 90 0, 4 34" 0:65 0. 2- 11 7 20.5 1. 1 2 0.15 38 0. 2, 0.01 7 days at 120F. 29.5 1.00 0.19 6 {routine 4S 0.00 g 0.02 7 days at 120F 41 1.08 0.07 H792 routine." 47 1 0.60 0.02 v ey l 2g 3&3 3.5%.. r9utine 7-dayseti20r. as 1304 051m- 6 inTa'bl' A, the above-data" in Table- B' shovr 7 further the beneficial retardation of loss of sp'eed that can be attainedinl accordance with our invention.

EXAMPLE 11) A batch of gelatino-silver-bromoiodide emulsion was prepared as described. by Trivelli and Smith; Phot. J. 79, 330 (1939), using a precipitation time of about 20 minutes (emulsion No. 11,. pagev 330)., except. that just before the fin'al digestion. of the emulsion potassiumchloroaurate; and. sodium thiocyanate were-added to the: emulsion. in: they concentrations show-n- Example- 1. A- portionidf theemulsion was coated on cellulose acetate film and dried. Thefilm; was cutinto two portions and the one portion exposed-and developed in the routine manner shownt in Example '1' while the other portion: was

Table 0' Water-insolubleii i i fi K T A er ina igeseeping r0at- Speed tion (mg. of gold-per nient ('l/i) Gamma 1000;g.' ofsilver nitrate) routine... 4'31 0. 04 0.02. L

{7 days at as 1 .14- 0.07 rou no: 43- 562 0.03} VIL mi y at 120'F 34', 1.12 0,09 rou ins--.- 41 0.63 0.02 VIL 19 {7 days at 120m... :32 g6 l8 rou ine;' 4. l .03 10 {7 da s at none... 35 l. 00 0. 1s rou ine 54 0. 48 0.03 20 {7 days at 120F 4s 0. as 0.19 6 X 20 routine; 50 0.59 0.03 i 'z'days atl20F 49 0.95 0.20

As in Table A, the above data in Table C show further the beneficial retardation ofloss of speed that can .be attai-ned inpaccordance with'rourdnvention.-

Any water=insoluble gold compound-- having.

solubility. in water notgreater "thajmtheequiva lentof 10mg. ofgold-per-1 00'=ml. of watersat' 25 C; can be employed: to: add to: the gold-900mpound-sensitized emulsions after final digestion butprior to coating the emulsions, in accordance,

with our invention. Many ofsuchwater-insolue ble; gold compounds are described lin-theachemi- .1. 76.- Still other water-insoluble gold compounds can Results are recorded in beprepared as described in the following examples;

EXAMPLE 2 S C-SAu 1% Ca Cl A solution containing 1 g. of auric chloride in cc. of 95% ethyl alcohol was added to 50 cc. of 95% ethyl alcohol containing 1.81 g. of 3-methy1- 2(3)-thiobenzothiazolone (prepared by heating 2 methylmercaptobenzothiazole metho-p-toluenesulfonate in boiling pyridine). The above formulated product separated as a white solid at once. The reaction mixture was stood at about C. for several hours and then chilled.

The white solid was filtered from the chilled mixture and washed on the filter with 95% ethyl alcohol. The yield of colorless crystals was 98% crude, and 73% after one recrystallization from acetic acid.

EXAMPLE 3 EXAMPLE 4 A solution containing 0.34 g. of auric chloride in 10 cc. of 95% ethyl alcohol was added to a solution containing 1.11 g. of 3-ethyl-5-[(3-ethyl- 2(3) -benzoxazolylidene) ethylidenel rhodanine in cc. of pyridine and 25 cc. of 95% ethyl alcohol. A reddish solid separated at once. The reaction mixture was stood at about 20 C. for several hours and then the solid was collected on a filter and Washed with 95% ethyl alcohol. The yield of product was 63% crude and 12% after two recrystallizations from nitromethane. The reddish crystals had melting point 231-232 C. with decomposition.

EXAMPLE 5 Y A solution containing 0.5 g. of auric chloride in 10 cc. of ethyl alcohol was added to a hot suspension of 1.61 g. of 3-ethyl-5-(3-ethyl-2(3) benzothiazolylidene)rhodanine in 25 cc. of acetic acid. The reaction mixture was stood several hours at about 20 C. and the precipitated solid was filtered off and washed on the filter with 95% ethyl alcohol. The washed solid was extracted with 180 cc. of hot nitromethane. Upon chilling the hot extract, the crystals which formed were filtered off and recrystallized from 155 cc. of nitromethane. The yield of golden yellow crystals was almost EXAMPLE 6 l LA/ C 5H5 AuCli EXAMPLE 7 Hz H:

CH3 AuCh A solution containing 1 g. of auric chloride in 10 cc. of absolute ethyl alcohol was added to a solution containing 0.7 3 g. of 2- [2- l-piperidyl) vinyl] benzothiazole methochloride in 10 cc. of absolute ethyl alcohol. After chilling for one hour at 0 C. the solid which separated wa collected on a filter and washed with absolute ethyl alcohol. The yield was 94% crude and 67% after one recrystallization from nitromethane. The dark crystals gave a pale yellow solution in acetone.

EXAMPLE 8 m N I (12H; 02H5 Allah A solution containing 1 g. of auric chloride in 10 cc. of absolute ethyl alcohol was added to a solution containing 0.90 g. of 1,1'-diethyl-2,2'-

cyanine chloride in 20 cc. of absolute ethyl alcohol. A reddish solid separated at once. After chilling for one hour at 0 C., the solid was collected on a filter and washed with absolute ethyl alcohol. The yield of dye was 72% crude and 45% after one recrystallization from nitromethane. The dark green crystals gave a pink solu- 75 tion in acetone.

l C2 15 2 35 Qh A solution containing 1 g. of auric chloridein 10 cc. of absolute ethyl alcohol was added to a suspension of 1.18 g. of 3,3'-diethyl-4,5, l',5' =di- .benzothiacyanine chloride in 40 cc. of absolute ethyl alcohol. A dark solid was formed at once. After .chilling for one hour at C. thesolid was .collected on a filter and washed with absolute ethyl alcohol. The yield was 93% crude and 74% after on recrystallization from nitromethane. The blue crystals gave a yellow solution in acetone.

, EXAMPLE 1o N 02H, Allol4 EXAMPLE 11 A solution containing 1 g. of auric chloride in cc. of absolute ethyl alcohol was added to a suspension of 0.93 g. of '3,3-diethylthiacyanine chloride in cc. of absolute ethyl alcohol. A pale orange solid separated at once. After chilling for one'hour at 0 C., the solid-was collected on a filter and washed with absolute ethyl alcohol. The yield of dye was 56% crude and 38% after one recrystallization from nitromethane. The deep red crystals with a blue reflex gave a pale yellow solution in acetone.

In a manner similar to that shown in Examples 2 to 11, other similar organic water-insoluble gold compounds can be prepared. In the heterocyclic nuclei ofthe organic gold compounds v set forth in Examples 2 to 11 one or more of the hydrogen atoms can be replaced by a chlorine, a bromine, or an iodine atom or by an alkyl oraryl group, e. g. methyl, ethyl, phenyl, etc.

Our invention can be practiced on photographic silver halide emulsions which have been sensitized by digesting the emulsions in the presence of either water-soluble or water-insoluble goldcom ounds. As shown above the S6I $i i a emulsionsfat least one water-soluble gold torn pound, .eQg. any of the water-soluble gold comset forth above, is added to the emulsion :prior to .or during the final digestion. Advantageouslythe concentration of the gold compound is equivalent to from 2.5 to 1000 mg of gold per 1l00 g. of silver nitrate used in preparing the emulsion. Most advantageously .a concentration of water-soluble gold compound equivalelllt P m 2 to 9 0f g l P 98??? of silver nitrate used in preparing the emulsion is employed. 7

Advantag eously vthe level of pH during the e tion t e emulsion, in we P esen of e -wate -so a l eld mp un is "m inta n at or below 9, although this is not essential.

G n ral y sp n i eb t' e u t ta i by dige tin t emulsions a a pH 9 ire'm t 9 i the ess nce Q th t -s uble gol compound. pigestion of the emulsions rin the esse e 9 e aci cqm wn is damaeq sle c e a rq 4 5 -a t 1ws the teens-raters an b- -ia A iin eretu rangeof '50 to C. ordinarily gives the best results.

Advantageously the emulsions sensitized by digesting with the water-soluble gold compounds are digested in the additional presence 'of'at least one sulfur compound, e. g. a sulfur sensitizer, for instance anorganic compound con taining a .-C=S or a group. Typical of such sulfur sensitizers are:

Normal gelatins contain small amounts of vsulsfurcompounds, such as thiosinamine or .allylisoth iocyanate, but-it. is nevertheless .irequently advantageous co to the gelatineniulsions additional sulfur sensitizers.

Beneficial efiects are also obtained by digesting the emulsions which zaresensitized by dig estion in the presence of a waterr-solublegold compound, in theadditional presence.ofatleastone metal or ammonium thiocyanate, e. -g..alk ali metal thiocyanates ('e. 'g. sodium or potassium thiocyanate), alkaline earth metal thiocyanates (e. g. calcium, strontium .thiocyanate, etc), cad- .mium thiocyanate, ammonium thiocyanate, etc. Of course, 'thiocyanatescontaining cations. which cations are known to have, in themselves, .a'. deleterious efiect on silver halide emulsions should be avoided. Otherwise, the beneficial .efiects-attained with the -,-thiocyanates would be partially nullified by the deleterious action of the cation. Thus iron thiocyanate which contains the iron cation should be avoided. One or more sulfur sensitizers or one or more thiocyanates selected from the group consisting of metal or ammonium thiocyanates can be employed. One or more sulfur sensitizers can be employed in conjunction with one or more thiocyanates containing a cation selected from the group consisting of metal and ammonium cations. The sulfur sensitizers and thiocyanates are advantageously incorporated in the emulsions in the form of their solutions in a suitable solvent, such as water, methyl or ethyl alcohol.

The sulfur sensitizers can be incorporated in the emulsions at any stage of the preparation of the emulsions, e. g. during precipitation of the silver halides, during the first digestions (ripening) or during the second digestion of the emulsions. When incorporating metal and ammonium thiocyanates in the emulsions prior to washing, the amount can vary widely. Advantageously, however, an amount of thiocyanate equal to from about to about 75 g. per kilogram of silver nitrate used in preparing the emulsion is employed. If the thiocyanate or sulfur sensitizer is not added until later in the preparation, e. g. after Washing, it is advantageous to employ, in the case of the thiocyanates, an amount equal tofrom about 0.1 to about 10 g. per kilogram of silver nitrate used in preparing the emulsion and in the case of the other sulfur sensitizers, an amount equal to from about 0.01 to about 10 g. per kilogram of the silver nitrate used in preparing the emulsion.

It is advantageous to digest, i. e. to heat treat, the emulsion with both the water-insoluble gold compound and the sulfur sensitizer or thiocyanate present, at an appropriate temperature, e. g. at from 100 to 150 F. During digestion, i. e. the second digestion as contrasted with the first digestion or ripening, the pH of the emulsion is advantageously adjusted to between 5 and 7.

To sensitize emulsions with water-insoluble gold compounds, the procedures (e. g. pI-I, temperature, sulfur sensitizers, thiocyanates, etc.) set forth above for sensitizing emulsions with water-soluble gold compounds can be employed.

sensitizing dyes of all types can be employed to spectrally (optically) sensitize our new stabilized emulsions, e. g. erythrosin, Congo red, any of the sensitizing cyanine dyes (monomethine, trimethine, pentamethine, heptamethine, etc), and any of the sensitizing merocyanine dyes (see United States Patent 2,078,233, dated April 27, 1937, for example), any of the sensitizing hemicyanine dyes (see United States Patent 2,166,736, dated July 18, 1939, for example), any of the sensitizing hemioxonol dyes (see United States Patent 2,216,441, dated October 1, 1940, and United States Patent 2,165,339, dated July 11, 1939, for example), etc.

Our new stabilized emulsions can be coated in the usual manner on any suitable support, such as glass, cellulose nitrate film, cellulose acetate film, polyvinyl acetal resin film, etc. to desired thickness, and then set in the usual manner. Hardening agents, setting agents and supersensitizing combinations of sensitizing dyes or a supersensitizing combination of one or more sensitizing dyes and another substance can be added to the emulsions.

Emulsions in which the carrier for the silver halide is other than gelatin and which have been 12 sensitized by digesting in the presence of a gold compound can be stabilized in accordance with our invention. Among such non-gelatin silver halide emulsions are silver halide emulsions prepared using as the vehicle or carrier polyvinyl alcohol (polyvinyl alcohol is herein intended to include all water-soluble hydrolyzed polyvinyl esters containing an ester group content equivalent to from 0 to 5% by weight of polyvinyl ester) silver halide emulsions prepared using as the vehicle or carrier hydrolyzed polyvinyl acetate containing an acetate group content equivalent to from 59 to 71% by weight of poyvinyl acetate; silver halide emulsions prepared using as the vehicle or carrier polyvinyl acetals containing a large proportion of polyvinyl alcohol hydroxyl groups, e. g. polyvinyl acetaldehyde acetals containing polyvinyl acetaldehyde acetal group equivalent to at least by weight of polyvinyl acetaldehyde acetal and polyvinyl alcohol hydroxyl groups equivalent to at least 15% by weight of polyvinyl alcohol, polyvinyl propionaldehyde acetals containing polyvinyl alcohol hydroxyl groups equivalent to from 45 to 60% by weight of polyvinyl alcohol, and polyvinyl butyraldehyde acetals containing polyvinyl alcohol hydroxyl groups equivalent to from 60 to 80% by weight of polyvinyl alcohol, etc. Any polyvinyl compound, especially those containing only carbon, hydrogen and oxygen atoms, or those containing carbon, hydrogen, oxygen and amine nitrogen atoms or ammonium nitrogen atoms, which is soluble in a mixture of ethyl alcohol and water (containing from 0 to 50% by volume of ethyl alcohol) to the extent of 10 g. per 100 g. of solvent can be employed as the vehicle or carrier in preparing our non-gelatin silver halide emulsions. Moreover, any other resinous or colloidal material soluble in any ethyl alcohol-water mixture or in water, as stated above, can be employed in preparing our non-gelatin silver halide emulsions, e. g. soluble polyamide resins, such as described in United States Patent 2,384,072, dated September 4, 1945, and hydrol zed copolymers of vinyl esters and ethylene or propylene, such as described in United States Patent 2,397,866, dated April 2, 1946. Still further examples of col loidal materials which can be employed as vehicles or carriers in preparing our non-gelatin emulsions are hydrolyzed cellulose carboxylic esters, such as hydrolyzed cellulose acetate or hydrolyzed cellulose acetate propionate, containing from 19 to 33% by Weight of acyl groups, for example. Any cellulose compound, especially those containing only carbon, hydrogen and oxygen atoms, or those containing only carbon, hydrogen, oxygen and amino nitrogen atoms or ammonium nitrogen atoms, which is soluble in a mixture of ethyl alcohol and water (containing from 0 to 50% by volume of ethyl alcohol) to the extent of 10 g. per g. of solvent can be employed as the vehicle or carrier in preparing our non-gelatin silver halide emulsion.

In connection with the non-gelatin colloidal materials, such as polyvinyl alcohol, the silver halide emulsions can be prepared using gelling agents, such as phenols, e. g. orcinol, gallic acid, 2,4-dihydroxybenzoic acid, 4-chlororesorcinol, e-naphthol, phloroglucinol, 2,7-dihydroxynaphthalene, etc. Moreover, the non-gelatin silver halide emulsions can be prepared using silver halide dispersing agents, e. g. starch acetate, gum arabic, a copolymer of maleic anhydride and vinyl acetate, low viscosity methyl cellulose, water-soluble amino carbohydrate dispersing agents :te. g. diethanolamine cellulose :acetate or any other of these agents described *in United States Patent 2,360,238, dated October 10, 1944) amino resin dispersing agents (e. g. dimethylaminobenzaldehyde acetals of polyvinyl alcohol, or water-soluble polyvinyl acetals in which at least a part of the acetal groups are 4-formylphenyltrialkylammonium saltacetal groups, such as the polyvinyl acetal of 4-formylphenyl trimethylammonium methylsulfate and other such compounds described in United 'States Patent 12,358,836, dated September 26, 1944), etc.

Polyvinyl-compound silver halide emulsions and their-preparation are described'in United States "Patents 2;286;216, dated June 16, 1942; 2,276,322, dated :March 17, 1942; 2276,3215, dated March 17, 1942;2311958, datedFebruarylG, 1943; 2,311,059, dated February 16, 1943; '2,36'7;511, dated :J anuary 16, 1945; 2,376,371, dated May 22, 1945 and 2,110,491,.dated'lvlarch 8,1938.

Non-gelatin proteins can also be employed as vehiclesorcarriers in preparing the silver halide emulsions which are stabilized in accordance-with our invention. Proteins, such as casein, soybeanbilization of photographic. silver halide emulsions 1 which have been sensitized by digestion in the presence 'ofsat least one gold compound (watersoluble or Water-insoluble) and in which the silver halide is principally silver bromide, but canbe employed with anysilver halide emulsion which has been so sensitized, particularly with the customary silver chloride, silver chloro- :brom-ide, silver chlorobromoiodide, silver chloroiodide, silver bromide and silver bromoiodide developing-out emulsions which have been so sensitized. By the term photographic silver halide emulsion in which the silver halide is principally silver bromide, we mean a photographic silver halide -emulsion i-n which from 60 to 100% of the weight of the silver halide is silver bromide.

Eastman Kodak Companys-D-li) developer has the "following composition:

Water liters 2.0 N-methyl-p-aminophenolsulfategrams.-- 8.8 Sodium sulfite, desiccated do 384.0 Hydroquinone do 35.2 Sodium carbonate, desiccated do 192.0 Potassium bromide do 20.0 Water to make V liters 4.0

waterrnot greater than the equivalent of 1.0 mg.

of gold per 100 ml. of Water at 25 C. and not less .14 thanrtheequivalentofiolcfilm feo diper 190112 1 of water at;2-5:C.

.Arprocesszforstabilizin -a ainst loss OfxSPQ agglqotographicgelatinmsilver-halide.develqll n out emulsion whichhas beenss nsiti d by di esting the emulsion in the presence-of agold compound comprising adding to the gold-compound- .sensitized emulsion after the final digestion of the emulsion, but prior to coating the emulsion on *asupport, a water-insoluble goldcompound which has :a solubility in water not-greater ,than the equivalent of 1.0.mg. of goldper l00,ml..of water at 25 (land not less than the ,theequivalent of (103mg. of gold per ml. of water at 25C.

3. .A, process for stabiliizng againstjlossof s eed a photographic, gelatinoesilver-halide developin out emulsion which has been sensitizedlbyjd gfisfiing the emulsion in the presence of agoldcompound, comprising adding to thegold-c omp oundsensitized emulsion, at a pH of from5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on asupport, a water-jinsoluble gold compound which has a solubility-in water not greater than the equivalent of 1.0;mg.

of gold per 100 ml. of water at 25 C. and not less than the equivalent of 0.03 mg. of gold per 100ml. of water at 25C.

4. A process for-stabilizing against loss of speed a photographic gelatino-silver-halide developingout emulsion in which the silver halide is principally silver bromide, which has'been sensitized by digesting the emulsion in the presence of a gold compound, comprising adding to the-goldcompound-sensitized emulsion at a pH of from S te-9, after the final digestion of the emulsion, but prior to coating the emulsion on "a ,support, a water-insoluble gold compound which has a solubility in water not greater than the 7 per 1000 g. of silvernitrate used. in preparing the emulsion.

5. A process for stabilizing a ainstloss .of speed a photographic gelatinoesilver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold compound, comprising adding to the.gold-compound-sensitized emulsion at a pH of 5 to 9, after the final digestion of the emulsion,.b.ut prior to coating the emulsionone support, awater-insoluble gold compound whichhas a solubility inwater not greater than the. equivalent of 1.0 mg. of gold per 100 ml. of water at 25C. and not less thanthe equivalent of 0.03 mg. of,goldp er 100 ml. of water at 25 C; the concentration .of the water-insoluble gold compound being equivalent to from 225 to 20 mg.;-per 1GOQ-g. of silver nitrate used in preparing theemulsion.

'6. A process for stabilizing against loss-of'speed a photographic, gelatinosilver-halide developing- .out emulsion inwhich-the silver halide'is-principa'lly silver bromide-which has been sensitized by digesting the emulsion in the presence of 'a gold compound and a sulfur sensitizer, comprising adding to the gold-compound-sensitized emulsion at'a pH of 5 to 9, after the final digestion of the emulsion, but prior to coating *the emulsion on a support, a water-insoluble gold compound which has asolubility in water :not greater than the equivalentcf 1.0 vmg. :of gold 15 per 100 ml. of water at 25 C. and not less than the equivalent of 0.03 mg. of gold per 100 ml. of water at 25 C., the concentration of the waterinsoluble gold compound being equivalent to from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

7. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold compound and a sulfur sensitizer, comprising adding to the gold-compound-sensitized emulsion at a pH of to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-insoluble gold compound which has a solubility in water not greater than the equivalent of 1.0 mg. of gold per 100 ml. of water at 25 C. and not less than the equivalent 010.03 mg. of gold per 100 ml. of water at 25 C., the concentration of the waterinsoluble gold compound being equivalent to from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

8. A process for stabilizing against loss of speed a photographic gelatino-silver-halide developingout emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the gold-compound-sensitized emulsion at a pH of 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-insoluble gold compound which has a solubility in water not greater than the equivalent of 1.0 mg. of gold per 100 ml. of water at 25 C. and not less than the equivalent of 0.03 mg. of gold per 100 ml. of water at 25 0., the concentration of the water-insoluble gold compound being equivalent to from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

9'. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the gold-compound-sensitized emulsion at a pH of 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-insoluble gold compound which has a solubility in water not greater than the equivalent of 1.0 mg. of gold per 100 ml. of water at 25 C. and not less than the equivalent of 0.03 mg. of gold per 100 ml. of water at 25 C., the concentration of the water-insoluble gold compound being equivalent to from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

10. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the gold-compound-sensitized emulsion at a pH of from 5 to 9, after final digestion of the emulsion, but prior to coating the emulsion on a '16 support, a water-insoluble gold compound having the following formula:

in a concentration of from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

11. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide which has been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the gold-compound-sensitized emulsion at a pH of from 5 to 9, after final digestion of the emulsion, but prior to coating the emulsion on a support, a water-insoluble gold compound having the following formula:

U 2 5 (lg H5 AuCh in a concentration of from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

12, A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide which has been sensitized by digesting the emulsion in the presence of a gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, comprising adding to the goldcompoundsensitized emulsion at a pH of from 5 to 9, after final digestion of the emulsion, but prior to coating the emulsion on a support, aurous sulfide in a concentration of from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

13. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has been sensitized by digesting the emulsion in the presence of potassium chloroaurate, thiosinamine and sodium thiocyanate, comprising adding to the potassium-chloroaurate-sensitized emulsion at a pi-I of from 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-insoluble compound having the following formula:

in a concentration of from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

14. A process for stabilizing against loss of speed a photographic gelatino-silver-bromoiodide developing-out emulsion in which the silver halide is principally silver bromide, which has beensensitized by digesting the emulsion in the presence of potassium chloroaurate, thiosinamine and sodium thiocyanate, comprising adding to the potassium-chloroaurate-sensitized emulsion 17 at a pH of from 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, a water-insoluble compound having the following formula:

the potassium-chloroaurate-sensitized emulsion at a pH of from 5 to 9, after the final digestion of the emulsion, but prior to coating the emulsion on a support, aurous sulfide in a concentration of from 2.5 to 20 mg. per 1000 g. of silver nitrate used in preparing the emulsion.

18 16. The emulsion obtained by the process of claim 1. a

17. The emulsion obtained by the process of claim 3.

18. The emulsion obtained by the process of claim 4.

19. The emulsion obtained by the process of claim 6.

20. The emulsion obtained by the process of claim 14.

HENRY C. YUTZY. JOHN A. LEERMAKERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,399,083 Waller et al Apr. 23, 1946 FOREIGN PATENTS Number Country Date Great Britain Sept. 20, 1948 

1. A PROCESS FOR STABILIZING AGAINST LOSS OF SPEED A PHOTOGRAPHIC SILVER HALIDE EMULSION WHICH HAS BEEN SENSITIZED BY DIGESTING THE EMULSION IN THE PRESENCE OF A GOLD COMPOUND, COMPRISING ADDING TO THE GOLD-COMPOUND-SENSITIZED EMULSION AFTER THE FINAL DIGESTION OF THE EMULSION BUT PRIOR TO COATING THE EMULSION ON A SUPPORT, A WATER-INSOLUBLE GOLD COMPOUND WHICH HAS A SOLUBILITY IN WATER NOT GREATER THAN THE EQUIVALENT OF 1.0 MG. OF GOLD PER 100 ML. OF WATER AT 25* C. AND NOT LESS THAN THE EQUIVALENT OF 0.03 MG. OF GOLD PER 100 ML. OF WATER AT 25* C. 